Patients receive interleukin-12 intraperitoneally once weekly. Treatment repeats every 4 weeks for 4 courses in the absence of disease progression or unacceptable toxicity. Patients with stable or responding disease receive 2 additional courses. Quality of life is assessed at baseline; prior to weeks 2, 4, 8, 12, and 16 of treatment; when patients are informed of their disease response; and then 2 weeks later. Patients are followed every 2 months for 1 year and then every 3 months for 1 year.